Catalytic smoke eliminator for high temperature self-cleaning ovens



3,470,354 ERATURE 7 3 S W U I m mm I T N t w nc Lo C mum l 1 F Sept. 30,1969 CATALYTIC smoxn ELIMINATOR FOR HIGH TEMP FIG.3.

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INVENTOR Carl W. Tilus W! ATTORNEY FIG.5.

FIG.6.

4 WITNESSES $2M $95M United States Patent 3,470,354 CATALYTIC SMOKEELIMINATOR FOR HIGH TEMPERATURE SELF-CLEANING OVENS Carl W. Tilus,Mansfield, Ohio, assignor to Westinghouse Electric Corporation,Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 19, 1967, Ser.No. 676,446 Int. Cl. F27d 11/00; A21d 1/20 US. Cl. 219393 ClaimsABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of theinvention The invention relates to the art of catalytic oxidizing unitsfor use in self-cleaning domestic ovens for eliminating smoke dischargeduring a cleaning operation of the oven.

Description of the prior art Of the self-cleaning (i.e., heat-cleaning)domestic ovens which are currently marketed so far as I know, one groupoperates with an average control temperature for the cleaning cycle inthe order of about 880 F. for an extended period of time, While anothergroup uses a substantially higher control temperature in the order ofabout 1050 F. for a substantially shorter period of time. The lattergroup of ovens, while in total producing no more (and perhaps less)smoke discharge for a single cleaning cycle, does produce, under heavysoil loads, the smoke and other combustion products at a high rate whichgives visual evidence of the smoke issuing from the venting outlet.Accordingly, for the purpose of avoiding objections from some quartershaving an influence on the marketing of such ovens, it is desirable thata catalytic oxidizing unit be provided which has a faster rate ofoxidizing the combustion gases than those currently used in the notedlatter group of ovens. It is further desirable that the catalyticoxidizing unit be compatible in structure with the oven structuralarrangement of an even of the character adapted to carry out thecleaning operation at the high temperature, as disclosed in KastovichUS. patent application Ser. No. 552,663. Finally, the oxidizing unitshould be of reasonable cost.

SUMMARY OF THE INVENTION The gist of the invention is the provision of apair of closely spaced walls of extended area defining a catalyticoxidizing passage therebetween by the provision on at least one of thefacing wall surfaces of a catalytic coating. The air flow pattern isradially in between the peripheral edges of the facing walls to acentral outlet. The heating means for activating the catalyst during aself-cleaning operation is a heating element closely adjacent one of theWalls.

In modifications of the basic structural arrangement, means may beprovided for enlarging the cross sectional area of the passage adjacentthe outlet to accommodate the confluence of the exhausted gases passingto the outlet, I

and the provision of means on one or the other or both ice of the wallsfor partially disrupting a straight flow path of the exhaust gasesbetween the spaced walls.

DRAWING DESCRIPTION FIGURE 1 is a partly broken side view of a rangehaving a heat-cleaning oven provided with a catalytic oxidizing unitaccording to the invention;

FIG. 2 is a vertical sectional view corresponding to one taken along theline II-II of FIG. 3;

FIG. 3 is a partly broken top view of an oven liner having an underlyingoxidizing unit according to the invention;

FIG. 4 is a vertical sectional view corresponding to one taken along theline IV-IV of FIG. 3 and enlarged relative to the FIG. 2 section;

FIG. 5 is a top view of a lower wall of an oxidizing unit provided witha modification;

FIG. 6 is a vertical sectional view corresponding to one taken along theline VIVI of FIG. 5; and

FIG. 7 is a vertical section taken through the center of the oxidizingunit adjacent the outlet vent and illustrating a modification adapted toaccommodate the confluence of combustion gases adjacent the outlet vent.

PREFERRED EMBODIMENTS An oven provided with a smoke eliminator accordingto the invention may be embodied in a cooking range of the generalcharacter illustrated in FIGURE 1 for example. The oven cooking cavity10 in which the cooking operations and the heating-cleaning operationtakes place is defined on the top, bottom, sides and rear by an ovenliner 12, and on the front by the oven door 14. Thermal insulation 16 isprovided around the liner walls and in the oven door 14. The heatingelements for the oven cavity include the lower element 18, normallyenergized for baking purposes, and the upper heating element 26 normallyused for broiling purposes. These elements are connected throughreceptacles at the liner rear wall 22 to a source of electrical power ofthe character normally used for cooking ovens. In accordance with thenoted Kastovich patent application, the broil element 20 also serves asthe source of heat for the heat-cleaning operation of the oven.

The catalytic smoke eliminating unit generally designated 24 ispreferably located in the top portion of the oven immediately below thetop wall 26 of the oven liner. In essence it includes a pair of closelyspaced, extended area, facing walls 28 and 30, at least one of the wallsbeing provided with a catalytic coating on its surface facing theopposing wall. The combustion products to be exhausted from the ovenduring heat-cleaning flow into the space between the walls at theperiphery of the walls and flow radially to the center of the space andthrough an outlet vent 32 into the room through an opening at one of thesurface cooking units.

Referring to FIGURES 2-4 which illustrate in some what more detail thestructural arrangement of the smoke eliminating unit, as there shown theupper plate 28 is generally rectangular and is provided with a centralopening 34 coincident with a central opening 36 in the top wall 26 ofthe oven liner. The outlet vent 32 is in the form of an upright tubewith a flanged lower end 38 secured in the liner wall opening 36.

The lower wall 30 of the eliminating unit is generally coextensive inarea with the upper Wall 28. The spacing between the upper and lowerwalls is provided by spacers 42 distributed throughout the passage 40 atsufficiently close intervals to hold the spacing during differentialexpafiision and contraction of the walls relative to each ot er.

The upper heater 20 is of serpentine character as best seen in FIG. 3.As viewed in plan, it is of open work character and has a peripheraloutline, as defined by its extremities, which bounds an area of thelower wall 30 coextensive with at least the major portion of the area ofthe lower wall. The heat energy produced by the heater activates thecatalytic coating 44 (FIG. 4) provided on one or both of the inner facesof the passage. The heater is hungfrom the lower wall 30 by means ofZ-shaped clips 46 supporting the front-to-rear runs of the heater. Theclips are preferably oriented to face one side so that the heater may bepulled forwardly out of its receptacle and then moved slightly to thatside to be removed from the oven.

It is noted while the catalytic coating is shown on both the upper andlower walls defining the passage 40, it may be desirable for reasons ofeconomy to coat only the one wall; preferably the lower wall 30 subjectto the greatest heating. Also, while a separate upper wall 28 isillustrated as defining the upper surface of the passage 40, in somecases the top wall 26 of the oven liner may be used as the upper wall ofthe passage.

The general pattern of air flow (illustrated by the broken line arrowsof FIGS. 1-4) from the oven cavity into the passage 40 is through theperipheral space at the edges of the two walls and then radially to thecenter of the passage and out through the outlet vent 32.

Modifications of the arrangement for the purpose of promoting smokeelimination through variations in the basic structure are illustrated inFIGS. 5-7. In FIG. 7, the lower wall 30 is shown with a depressed areaportion 48 opposite the outlet 32 for the purpose of accommodating theconfluence of the combustion products at the center of the passage.

FIGS. 5 and 6 illustrate an arrangement for varying the passage spacingtransverse to the direction of air flow at selected locations in thepassage. This provides a tortuous flow path for a part of the airflowing generally radially into the central outlet vent-32. The meansillustrated comprise upwardly directed embossments 50 in the lower wall30 in a pattern as shown in FIG. 5 for example. Thus a part of the airis constrained to follow the circuitous path illustrated by the brokenline arrows of FIG. 5 in passing from the peripheral edges of the wallsto the central outlet 32.

The catalytic coating 44 may be any of the catalytic materialsconventionally used for such purposes, such as a platinum material. Aspacing between the wall facing surfaces of the coatings, or coating andforming the passage in the order of .060 to .080 will give satisfactoryoperation.

It is noted that the system according to the invention has thecharacteristics of a high capacity fume abatement system because the airflow permitted is of substantial volume due to the use of a wide surfacearea of catalyst. It will also be appreciated that the structuralarrangement disclosed lends itself very well to the type ofheat-cleaning operation in which the upper heating element 20 of theoven is alone energized to provide the heat energy for the heat-cleaningoperation since the catalytic unit is located close to the heater forrapid temperature rise and has a passageway area generally coextensivewith the area bounded by the extremities of the upper heating element20.

I claim as my invention:

1. In a heat-claiming domestic oven of the type in which oventemperatures are elevated well above cooking range temperatures foreffecting the heat cleaning:

means defining an oven cavity in which gases are produced during aheat-cleaning operation;

an outlet vent for exhausting said gases from said oven cavity;

a catalytic oxidizing passage through which said gases are constrainedto flow in passing from said cavity to said outlet vent during saidcleaning operation, said passage being defined by horizontally disposedupper and lower, slightly spaced apart, extended surface area walls inthe extreme top portion of said cavity, at least one of the facingsurfaces thereof being coated with an oxidizing catalyst, the outletfrom said passage being generally centrally located relative to the areaof said walls and in communication with said outlet vent, the inlet forsaid oxidizing passage being generally coextensixe with the peripheraledges of said walls, so that the flow of said gases is generallyradially through said passage and then to said outlet vent, and;

means in the form of an electrical resistance heating element closelyattached to the bottom surface of said lower wall for heating said wallsduring said cleaning operation to a temperature providing etfectiveoxidization of said gases in said passage.

2. In an oven according to claim 1.

said heating means comprises an openwork heating element with aperipheral outline defined by its extremities bounding an areacoextensive with at least the major portion of the area of said passage.

3. In an oven according to claim 1:

at least one of said walls includes an area adjacent said outlet andspaced further from the facing area of said other wall, than the spacingbetween said walls throughout the remainder of said passage, toaccommodate the confluence of said gases in said area adjacent saidoutlet vent.

4. In an oven according to claim 1:

including means in said passage varying the passage spacing transverseto the direction of air flow at selected locations therein.

5. In an oven according to claim 4:

said means comprises portions embossed in at least one of said walls andprojecting toward the other of said walls.

References Cited 3,290,483 12/1966 Hurko 219-293 VOLODYMYR Y. MAYEWSKY,Primary Examiner U.S. Cl. X.R.

